Anchoring apparatus and methods for use

ABSTRACT

An apparatus for securing an implantable lead within tissue of a patient includes a base adapted to be secured to a patient&#39;s skull adjacent a craniotomy. The base has an upper surface and a lower surface with a central passage therebetween. The central passage is adapted to receive the implantable lead therethrough. The apparatus also has a cover that is releasably coupled to the base so as to substantially cover the central passage and capture the implantable lead therebetween. A first rotating member is also coupled with the base and the first member is rotationally movable so as to meet and engage the implantable lead at a plurality of positions within the central passage.

CROSS-REFERENCE

This application is a divisional of U.S. patent application Ser. No.12/056,752, now U.S. Pat. No. 8,038,685, filed on Mar. 27, 2008, whichis a non-provisional of, and claims the benefit of U.S. ProvisionalPatent Application No. 60/908,367, filed Mar. 27, 2007; the entirecontents of each of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to medical apparatus and methods, morespecifically to instrument immobilizers and even more specifically, butnot by way of limitation to an apparatus and methods for anchoring anintracranial probe or lead to the cranium.

Implanting medical devices within the cranium is an increasinglyimportant approach for treatment of disorders such as Parkinson'sDisease, essential tremor and dystonia. This approach may also be usedto treat a wide array of neuropsychiatric problems, such as depression,epilepsy, obsessive compulsive disorder, obesity and chronic pain. Mostof these devices interact with the brain by delivering current throughan implanted probe to modulate brain activity. In addition, infusion ofdrugs through a permanently implanted probe has been proposed as aprimary treatment, or as an adjunctive treatment to electricalstimulation, for Alzheimer's and Parkinson's Diseases, among others.

As part of the implant procedure, the probe must be stabilized in thebrain. Ideally, any prosthetic device is attached directly to the tissueon which it operates, in this case, the brain. Direct attachment ofelectrical and chemical probes to brain tissue is impractical. A moreeasily implementable solution is a system of flexible probes that bendand float with the brain as the brain moves within the cranial cavity.Such probes are secured to the cranium. In this manner, mechanicalforces from outside the cranium are prevented from acting on thebrain-to-probe interface.

There are a number of current techniques for securing a probe to thecranium. For example, in one approach, a permanently implanted probe isfixed by a sliding door which closes to form a slot just wide enough toslightly compress and grip the body of the probe. A common feature ofsuch devices is that they grip the probe somewhere within the craniotomyopening, and that the slot has a fixed orientation relative to thecranium.

In another approach, the probe passes through a narrow aperture at thecenter of a craniotomy opening The probe is held in place by a surgeonas it is bent over into a slot leading to the exit from the device.Hinged arms swing into place to narrow the slot and anchor the probewithin the slot.

Current anchoring devices are typically positioned over the craniotomyopening, and they are attached to the cranium with several peripheralscrews. An implantable lead is placed through the cranial opening andthe lead is gripped by two opposing thin bars. In some cases, it ispossible to damage the lead by crushing it between the thin bars. Itwould therefore be desirable to grip the lead with wider bars to moreevenly distribute the gripping force over a greater axial length of theimplantable lead. It would also be desirable to provide a more stablemounting for the skull-mounted portion of the anchoring device.Additionally, current devices often have a small opening for receivingthe lead and thus it would be desirable to provide an anchoring devicehaving a wider opening for the lead, to permit adjustment of leadposition for optimal placement, especially when using a largemulti-channel probe array, a feature shared by only a few currentlyavailable anchoring systems.

2. Description of the Background Art

Prior patents and publications describing anchors for cranial probesinclude: U.S. Pat. Nos. 4,328,813; 5,464,446; 6,044,304; 2004/0267284;2005/0192594; and WO 2004/026161.

SUMMARY OF THE INVENTION

The invention generally provides an anchor for securing an implantablelead within tissues in a patient. The terms “lead” and “probe” will beused interchangeably with one another in this disclosure, as will theterms “anchor base” and “cylinder.” Often the lead may comprise anelectrode or a catheter, and the lead is often implanted into braintissue through a craniotomy in the patient's skull. A current and/ortherapeutic agent may be delivered through the lead to the tissue andthe anchor is usually composed of materials that are compatible withmagnetic resonance imaging. The anchor may be fabricated from metalsthat do not interfere with MRI and/or polymers such as polyphenylenesulfide, polyetheretherketone (PEEK), polyetherimide, polyimide,polysulfone and the like.

In a first aspect of the present invention an apparatus for securing animplantable lead within tissue of a patient comprises a base that isadapted to be secured to a patient's skull adjacent a craniotomy. Thebase has an upper surface, a lower surface and a central passagetherebetween which is adapted to receive the implantable lead. Theapparatus also includes a cover that can be releasably coupled to thebase so as to substantially cover the central passage and also tocapture the lead therebetween. A first rotating member or door, iscoupled with the base and is rotationally movable so as to meet andengage the lead at a plurality of positions within the central passage.Rotating the door also adjusts the position of an opening within thecentral passage in which the lead may pass through and also closes orreduces the size of the central passage while still allowing the lead topass therethrough.

Often, the first rotating member comprises a removable insert that isadapted to releasably grip the lead and that may be received in arecessed region of the rotating member. The removable insert is usuallyadapted to be removably coupled to the first rotating member with arotationally actuated tool that may be coupled to the first rotatingmember. The first rotating member may have a surface defining a wedgeshaped or indented region that is adapted to receive and align the tool.

The apparatus may have a pin or rivet engaged with the first rotatingmember that secures the first rotating member to the base while allowingrotation of the first rotating member relative to the base. The firstrotating member may also have a surface that defines a receptacle thatis adapted to receive a tool for turning the first rotating member intoa desired position so as to engage the lead and fix the lead into aposition. The first rotating member may further comprise a resilient endthat is adapted to releasably grip the lead. The resilient end may liein the same plane as the first rotating member and may be composed of anelastomer. The resilient end often is constructed with a substantiallysolid core while sometimes it may be porous. Often the resilient endcomprises surface features that are adapted to capture the lead. Thesurface features may include a plurality of convex or concave regionsadjacent to one another or the surface features may be scallops.Sometimes the surface features may comprise a plurality of resilientfingers that extend outward from the resilient end. The surface featuresmay also comprise combinations thereof.

The apparatus may further comprise a ratchet mechanism that is adaptedto restrict the first rotating member to motion in one direction. Oftenthe apparatus also comprises a fixing element such as a set screw thatis adapted to immobilize the first rotating member. The apparatus alsooften comprises a second rotating member that is coupled with the baseand a spacer may be used to separate the first and second rotatingmembers from one another. The second rotating member is rotationallymovable so as to meet and engage the lead at a plurality of positionswithin the central passage. Rotating the second door also adjusts theposition of an opening within the central passage in which the lead maypass through and also closes or reduces the size of the central passagewhile still allowing the lead to pass therethrough. Usually, the firstand second rotating members are movable independently of one another andthey may be retained in the base with a retaining member such as a ring.Also, the first and second rotating members may lie in the base adjacentto one another. Sometimes the second rotating member comprises aremovable insert that is adapted to releasably grip the lead. The inserton the second rotating member may take the same form as the insert onthe first rotating member. Often the resilient end on the first rotatingmember lies in a plane between the first and second rotating members.

The apparatus may further comprise a locking mechanism coupled with thefirst and second rotating members. The locking mechanism locks the firstand second members together thereby preventing relative motiontherebetween. The locking mechanism may be a detent and comprise aprotuberance on either the first or second rotating member and areceptacle for receiving the protuberance on the other rotating member.These features allow the rotating members to snap into position with oneanother thereby ensuring the lead is gripped therebetween.

Often, the apparatus further comprises one or more tabs that extendradially outward from the base. The tabs are adapted to be secured tothe skull adjacent the craniotomy. The tabs often define apertures thatcan receive a fastener such as a screw, thereby securing the baseadjacent the craniotomy.

Sometimes the base is cylindrical and may be sized to fit at leastpartially within the craniotomy, and at least a portion of the base maybe securely press fit into the craniotomy. The base may comprise adiscrete upper and a discrete lower portion that are fastened together,or the base may be of unitary construction. The base may be recessed atleast partially into the craniotomy, or the lower surface of the basemay sit substantially flush with the top of the skull. The base may alsohave one or more receptacles that are adapted to releasably receive atleast a portion of the cover. Often, the upper surface of the basedefines one or more channels that are sized and shaped to accept thelead after the lead has been disposed therein. The base may also beadapted to receive and retain other surgical instruments such asinstrument positioning guides or other reference devices often usedduring neurosurgery. These other surgical instruments may releasablylock with a flange in the base, a retaining member in the base or anyother portion of the base or components therein.

Often the cover is adapted to be removably coupled to the base.Sometimes the cover comprises one or more legs that are adapted toreleasably snap fit into engagement with the base. Alternatively, thelegs may be disposed on the base or on a retaining member that fits inthe base. The cover may have a surface that defines one or more channelsthat are sized and shaped to accept the lead after it has been disposedtherein. One or more plugs may be placed into the channels or a gasketmay be disposed between the cover and the base in order to seal any gapstherebetween.

In another aspect of the present invention, a system for securing animplantable lead within tissue of a patient comprises an apparatus forsecuring the implantable lead within tissue. The apparatus comprises abase adapted to be secured to a patient's skull adjacent a craniotomy,the base having an upper and lower surface and a central passagetherebetween. The implantable lead is often disposed in the centralpassage. The apparatus also comprises a first rotating member coupledwith the base and having a removable insert adapted to engage the lead.A retaining pin may couple the insert with the first rotating member.The first rotating member is rotationally movable so as to meet andengage the lead at a plurality of positions within the central passage.Rotating the door also adjusts the position of an opening within thecentral passage in which the lead may pass through and also closes orreduces the size of the central passage while still allowing the lead topass therethrough. The system also includes a tool having a proximalend, a distal end and a handle, the tool being adapted to introduce andremove the removable insert to or from the first rotating member.

Often the tool also comprises a pin disposed near the distal end that isadapted to retain the insert when the insert is decoupled from the firstrotating member. The tool is usually adapted to be rotated so as tosimultaneously engage the insert and withdraw the retaining pin from theinsert. The tool may have an angled surface that facilitates seating ofthe tool against the first rotating member.

The system may also include a cover that can be coupled to the base soas to substantially cover the central passage and also to capture thelead therebetween. The system may also comprise a potting material thatis used to fill gaps between the base and the craniotomy in order toreduce or eliminate leakage of body fluids, such as cerebral spinalfluid (CSF), from around the base.

In another aspect of the present invention, a method of securing animplantable lead into tissue of a patient comprises positioning a basehaving an upper surface, a lower surface and a central passagetherethrough, adjacent a craniotomy in a skull of a patient. The basemay be secured adjacent the craniotomy and to the skull and animplantable lead is inserted through the central passage into thetissue. Rotating a first rotating member that is coupled to the basemoves the rotating member so that it meets and engages the implantablelead at a plurality of positions within the central passage.

The method may also comprise the step of rotating a second rotatingmember that is also coupled to the base so as to meet and engage thelead at a plurality of positions within the central passage therebysecuring the lead in the tissue. Rotating the second door also adjuststhe position of an opening within the central passage in which the leadmay pass through and also closes or reduces the size of the centralpassage while still allowing the lead to pass therethrough. The methodmay also include rotationally adjusting the first and second rotatingmembers in order to capture the lead therebetween or to release the leadtherefrom. Often the method includes attaching and/or removing an insertthat is adapted to engage the lead and that is coupled to the first orsecond rotating members.

The method may also comprise inserting one or both of the two rotatingmembers into a secure base ring intraoperatively. In early stages of thelead implantation procedure, a wide lumen is available. After the leadis placed, an opening in such rotating members allows them to passaround the lead and rest in the base, and grip the lead. The method mayfurther comprise retaining the two rotating members within the base byinterlocking a retaining member placed over the rotating members andwithin the base, thereby restricting axial movement of the rotatingmembers relative to the base.

Sometimes securing the base comprises press fitting at least a portionof the base into the craniotomy and often securing the base comprisescoupling the base to the skull adjacent the craniotomy with a fastenersuch as a screw. Sometimes securing the base comprises recessing atleast a portion of the base in the craniotomy, or the base may becoupled adjacent the craniotomy such that a bottom surface of the baseis substantially flush with the craniotomy.

Usually, a cover is engaged with the base so as to substantially coverthe central passage and capture the implantable lead therebetween. Thecover and/or base may have channels which can accept the lead afterbeing positioned therein. Often the first and second rotating membersare locked and this may be accomplished by threadably engaging therotating members with a set screw or by using detents in order toprevent relative motion therebetween. Sometimes, the lead may be bentinto a channel that is defined by a top surface of the base and apotting material may be applied in order to fill gaps between the baseand the craniotomy, thereby reducing or eliminating leakage of bodyfluids such as CSF from around the base.

These and other embodiments are described in further details in thefollowing description related to the appended drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D illustrate cross-sections of several anchor assemblyembodiments having fixation tabs that allow the anchor to be placedwithin a craniotomy at varying depths.

FIG. 1E shows an anchor attached to a patient's cranium.

FIGS. 2A-2G show top and cross section views of rotating doors.

FIGS. 3A-3F show alternative embodiments of the grip bars.

FIGS. 4A-4F show alternative embodiments of the rotating doors.

FIG. 5A shows a top view of the cylinder without the rotating doors.

FIG. 5B shows a side view of an exemplary embodiment of a cover.

FIG. 5C shows a bottom view of an exemplary embodiment of a cover.

FIG. 6A shows a cross section view of an assembled anchor with rotatingdoors.

FIGS. 6B-6K show the components of the anchor depicted in FIG. 6A.

FIG. 7A shows an alternative embodiment of a mechanism for retaining themoving members within the cylinder.

FIG. 7B shows a bottom view of the anchor assembly in FIG. 7A.

FIGS. 8A-8C show an anchor base of unitary construction.

FIGS. 8D-8M show various components in various stages of assembly withthe anchor base of FIGS. 8A-8C.

FIGS. 9A-9C illustrate the use of set screws to lock the rotating doorsin position.

FIGS. 10A-10J show the use of a tool for placement and removal ofinserts into the rotating doors.

FIGS. 11A-11D show side views of a tool as it us used to insert, place,attach and detach inserts into the anchor.

FIGS. 12A-12C show an alternative embodiment of rotating doors that areadapted to pass around a placed lead intraoperatively and snap together.

FIGS. 13A-13C show an alternative embodiment of the anchor base whichmay be used with the doors of FIGS. 12A-12C.

FIGS. 14A-14E illustrate exemplary embodiments of retaining memberswhich hold the rotating doors in the anchor base.

FIGS. 15A-15D illustrate an exemplary embodiment of a retaining memberwhich retains the rotating doors and the cap.

FIG. 16 illustrates an exemplary embodiment of an anchor base withrotating doors that are held in place with a retaining member.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings like numerals describe substantially similar components.Now turning to FIG. 1A is a cross section exploded view of the anchorassembly, showing the probe 5, cap 200, and cylinder body 10, alsoreferred to as an anchor base in this application, assembled with partsthat grip the probe. In this embodiment, the radial tabs 20 are elevatedrelative to the bottom surface of base 10 so that the cylinder body 10may be recessed into a craniotomy. The cylinder 10 is fixed to thecranium by screws which pass through openings 25 in tabs 20 and securethe tabs to the cranium. In an alternative embodiment, the cylinder mayhave ridges, protrusions or other surface features (not shown) whichgenerate a friction fit with the wall of the craniotomy, in conjunctionwith or in lieu of the radial tabs. Rotating doors 110 and 120 are shownrotated to a position such that the grip bars 70 are positioned to gripthe probe 5. In the section shown in FIG. 1A, the grip bars 70 arepositioned by removable inserts 140 and 150, which in turn are capturedin the doors 110 and 120 by rotating rivets 130. An upper rivet plate134 and a lower rivet plate 136 coupled to rivet 130 help lock theinserts into position. A ring-like spacer 16 separates doors 110 and120. The cap 200 has legs or pins 220 with catches 225 which snap intoreceiving sockets 40 within the cylinder 10. The receiving sockets 40not only provide fixation for a cap, but also provide a site andmechanism for attaching other instruments to the device. Examples ofother devices that could be attached thereto include positioning guidesor other reference instruments commonly used during neurosurgery.

The grip bars 70 may be made of a soft material, for example anelastomer, such as silicone rubber, polyurethane, or Santoprene™, orthey may be made of the same material as the doors. Grip bars 70 may beporous or have holes running through them to make them compressible.Pores could be produced by many methods, including gas bubbles formingduring the curing process, dissolving filler materials, or bywithdrawing filaments introduced at the time the bars are formed ormolded. During implantation, the probe 5 is placed intracranially, andthe rotating doors 110 and 120 are rotated to place the grip bars 70against the probe 5. The probe 5 is bent to course along a groove 30 onthe superior surface of the cylinder 10, and onto the surface of thecranium. The cap 200 is then lowered so that pins of the cap 220 areinserted into sockets of the cylinder 40, and the cap presses againstthe probe 5. In some embodiments, a groove in the cap 210 wraps aroundthe probe 5. As the cap is lowered, pins 220 and protrusions from thepins 225 are displaced towards the center of the cylinder by catches 45,until the protrusions snap outward under the catches, retaining the cap.In other embodiments, the cap may have an elastomeric gasket shaped soas to seal the space between the cap and the base, except for allowingpassage for the probe through one set of grooves 30 and 210. In otherembodiments, the elastomeric gasket shall leave all sets of groovesopen, and the unused probe passages are filled with separate plugs withradial dimension similar to the probe.

FIG. 1B shows the embodiment of FIG. 1A with the probe 5 positionedintracranially, and the cap 200 snapped into the closed position. Inthis embodiment, the tabs 20 are elevated so that cylinder 10 may berecessed in the craniotomy allowing the top of the cylinder to besubstantially level with the cranium. Such an embodiment has theadvantage that the top of the cap extends minimally above the cranium.

FIG. 1C shows an alternative embodiment of the assembly shown in FIGS.1A-1B, in which the cylinder 10 is partially recessed into the cranium.FIG. 1D shows an alternative embodiment of the assembly shown in FIGS.1A-1C, in which the tabs 20 are positioned so that the lower surface ofthe cylinder 10 is at the level of the outer surface of the cranium.Such an embodiment has the advantage that the craniotomy opening needonly be as large as the inner lumen of the cylinder 10. The rotatingdoor grip mechanism provides the particular advantage that if the probe5 is inserted through the center of the device as shown in FIG. 1B, thedoors may be rotated together, thereby rotating the probe while stillretaining vertical fixation.

FIG. 1E illustrates the anchor base or cylinder 10 attached to apatient's cranium C. In FIG. 1E, anchor 10 is positioned over acraniotomy so that a portion of the anchor fits within the craniotomyopening in order to reduce the portion of anchor 10 protruding out ofthe patient's cranium C. Fixtures F such as screws removably couple theanchor 10 to the cranium and a lead 5 is place through the centralopening of the anchor 10 into the patient's brain B. A cover 200 maythen be snap fit into engagement with the anchor 10, thereby capturingthe lead 5 in a desired position.

FIG. 2A shows the lower rotating door 120, apart from the rest of theanchor. The door is a disk with a large cutout 122 within its interior.Along one edge of the cutout is a bar 70 which can grip the probe placedin an intracranial position. Near the bar is a ledge depressed into thedoor 80 into which a gripping insert can be placed. The insert isretained from movement towards the open portion of the disk byterminating the depression at two stops 85. FIG. 2B shows both rotatingdoors overlayed, with the both rivets 130 in the open position and bothinserts removed. In this configuration a relatively large opening in thecenter of the anchor is available for the probe or any related test oraccessory instrumentation.

FIG. 2C shows the upper rotating door 110 with the rivet 130 in theclosed position, and gripping insert 140 in place. The upper door alsohas a cutout 112, a gripping bar 70 and a place for seating the insert.The insert 140 rests on the depressed ledge 80. Motion of the inserttowards the open part of the door 140 is prevented by the stops 85, asin the lower door. Motion of the insert up out of the ledge, or rotationof the insert out of the ledge is prevented by the rivet 130. The upperplate of the rivet 134 is a partial disk. When it is in the closedposition, as shown in FIG. 2C, the upper plate covers the edge of theinsert, so that it is locked into place on the depressed seating ledge80. When it is open, the insert may be removed. The upper plate hasthree sockets 132 which may accept prongs from an insertion and removaltool, in order to rotate the rivet. A lower plate of the rivet 136 issimilar to the upper plate 134 and also helps hold the insert. Lowerplate 136 may be seen in FIG. 1A.

FIG. 2D shows a side view of the two rotating doors 110, 120, with theinserts 140, 150 in place, and the rivets in the closed position. Whenthe rotating doors 110, 120 are rotated, the inserts are pushed towardeach other by their corresponding doors. FIG. 2E shows the two rotatingdoors 110, 120 overlayed, with the inserts locked in place by the rivets130. FIG. 2F also shows the two rotating doors overlayed, with theinserts removed and the doors opened to their maximum aperture. FIG. 2Gshows both top and side views of the two inserts 140 and 150. The heador top portion 164 of insert 150 along with the head or top portion 162of insert 140 is seen in the side view of FIG. 2G. The divots in theinserts 165, 166 accommodate the rivets. When the rivets are rotatedinto the closed position, the tails of the inserts 160 fit between thehead of the rivet 134 and the seating depression in the rotating door80. When the inserts are in place, their grip bars 70 are continuouswith the grip bars of the rotating doors. The tails of the inserts 160sit in recessed ledges 80 in the rotating doors.

FIGS. 3A-3F show alternative embodiments of the grip bars 70, withgreater contact between the grip bars and the probe compared to theembodiment shown in previous Figures. Only views from above are shown.In FIG. 3A, the grip bars are scalloped to conform to the shape of theprobe, and the spacing between scallops is less than the diameter of theprobe, allowing many prospective positions where the probe could beplaced. In FIG. 3B, the grip bars are also scalloped, but with a shapecomplementary to the shape in FIG. 3A. This shape generates as manyprospective positions as the shape in FIG. 3A, but instead of apposingthe probe with conforming surfaces, this shape contacts the probe at 4points, compared to two points in the embodiment shown in the otherFigures. In FIG. 3C, the grip bars completely surround the probe,generating fewer prospective fixation positions compared to theembodiments of FIGS. 3A-3B. In FIG. 3D, thin flanges or resilientfingers protrude from the grip bars, such that the flanges from one gripbar are out of phase or alternate with the flanges from the other gripbar. FIGS. 3E-3F are similar to the embodiment of FIG. 3D, except thatthe flanges on opposite grip bars are in phase with one another so thatthey oppose each other, rather than the out of phase or alternatingpattern seen in FIG. 3D. FIG. 3E has longer flanges, while FIG. 3F hasshorter flanges. These different embodiments illustrate examples of howthe contact area of the grip bar with the probe may be increasedcompared to the embodiments shown in the other Figures.

FIGS. 4A-4F show alternative embodiments of the grip bars 70, with oneor both grip bars attached directly to the rotating door 110, 120,without an insert or the possibility of removing a portion of the gripbar 70. In FIGS. 4A-4D, the grip bars are centered on a plane betweenthe rotating doors, as in FIG. 2D, while in FIGS. 4E and 4F, the gripbars 70 are centered in the planes of their respective rotating doors.When the grip bars are centered on a plane between the rotating doors,they do not transmit a bending moment to a probe inserted parallel tothe axis of the cylindrical anchor body, while the embodiment in FIGS.4E-4F the grip bars could potentially transmit a bending moment to sucha probe.

FIGS. 4A-4B show an embodiment with an upper rotating door 110 similarto the embodiments shown in FIGS. 2A-2G, while the lower rotating doorhas no insert, and its grip bar is one continuous member. FIG. 4A showsthe rotating doors in position to grip the probe, while FIG. 4B showsthe rotating doors opened to their maximum aperture. The maximumaperture of this embodiment is nearly the same as the maximum apertureillustrated in FIG. 2F, except near the center of the cylinder.

FIGS. 4C-4D, show an embodiment in which neither rotating door has aninsert, and both grip bars are single, continuous members. FIG. 4C showsthe rotating doors in position to grip the probe, while FIG. 4D showsthe rotating doors opened to their maximum aperture. In this embodiment,the maximum aperture is smaller than in the embodiments of FIGS. 2A-2Gand FIGS. 4A-4B.

FIGS. 4E-4F show an embodiment in which neither rotating door has aninsert, and

both grip bars 70 are single, continuous members, as in FIGS. 4C-4D.FIG. 4E is a cross section view, which shows that in this embodiment thegrip bars 70 are centered in the plane of their respective rotatingdoors. FIG. 4F shows that the maximum aperture of this embodiment iswider than any of the other illustrated embodiments, except near thecenter.

In other embodiments, the grip bars could be attached directly to therotating doors for their full length, without any inserts or rivets. Itwill be obvious to those skilled in the art that many other specificforms are possible.

FIG. 5A shows a top view of the cylinder or anchor base 10, without therotating doors. The anchor is fixed to the cranium by screws throughscrew-holes 25 in radial tabs 20. A relatively short set screw 50inserts into a threaded hole 56 to impinge upon the upper rotating door110, (not shown) and lock it into place. A relatively long set screw 52having a flat point 51 inserts into a threaded hole 56 to impinge uponthe lower rotating door 120, (not shown) and lock it into place. Anotherrelatively long set screw 54 having a cone point 55 inserts into athreaded hole 56 to impinge upon both rotating doors 110 and 120 (notshown) and lock them into place. In the illustrated embodiment, screws50 and 52 have a flat tip, and impinge upon the outer upper corner ofthe rotating doors, while the screw 54 has an angled tip, and impingesupon the flat edge of both rotating doors. Receiving sockets 40 havingcatches 45 are adapted to receive the cap thereby snap fitting the twocomponents together. Additionally, grooves or channels 30 radiallyextend outward from anchor 10 and provide a channel for holding the leadwhen the lead is captured between the anchor 10 and the cap.

Alternatively, one of the rotating doors could be held in place by aone-way ratcheting mechanism. In such an embodiment, a no-back pawl is abeam integrated with the anchor cylinder, in the plane of one of therotating doors. The outer edge of the corresponding rotating door hasthe gear teeth. The pawl permits the gear teeth to pass freely in thedirection which moves the grip bar 70 towards the probe, closing thedoor, but prevents the rotating door from opening Such an embodimentmakes fixing the doors faster, as only one set screw must be tightened,yet still permits the opening between the doors to be adjusted to anyangular position, multiple times if necessary.

FIG. 5B shows a cross section view of the cap 200. It is dome shaped.Three pins 220 protrude downward, one of which is visible in this view.FIG. 5C shows a bottom view of the cap. The shape is a dome, truncatedadjacent to pins 220 which protrude downward to snap into sockets 40 inthe cylinder 10. The dome-shaped disk is truncated adjacent to the pinsso that a tool may be inserted into the socket 40, alongside a pin 220to facilitate removing the cap 200 when necessary. In the preferredembodiment, grooves 210 in the cap 200 increase the area of the cap 200contacting the probe, compared to grooveless embodiments. FIG. 5C showsa bottom view of cap 200 highlighting grooves 210 and pins 220.

Initially the probe is gripped by the rotating doors and fixed intoposition. The probe is then bent to lay in grooves 30 on the uppersurface of the cylinder. The cap is lowered, with pins 220 sliding intosockets 40 and protrusions 225 from the pins snapping into place undercatches 45. When the cap is snapped in place, it presses upon the probe.In the preferred embodiment, grooves in the cap 210 increase the surfacearea of the cap in contact with the probe, increasing stability anddecreasing point pressure on the probe.

FIG. 6A shows an exemplary embodiment of an anchor base assembled withall of its components. FIGS. 6B-6K show the various components of theassembly in FIG. 6A. In FIG. 6A, the anchor base is composed of upper 12and lower 14 portions. In the illustrated embodiment, radial tabs 20 areattached to the upper portion 12 of the cylinder 10, so that thecylinder may be recessed into the craniotomy opening In otherembodiments the tabs may be attached to the lower portion 14 of thecylinder 10. A shelf 26, which retains the moving members within thecylinder, is integrated into the lower portion of the cylinder 14. Theupper portion 12 of the cylinder is the more massive, because it mustcontain the threaded holes 56 for the set screws (seen in FIG. 6B).Within the cylinder the upper 110 and lower 120 rotating doors areseparated by a spacer ring 16. The upper 12 and lower 14 portions of thecylinder are attached by an adhesive. In alternative embodiments, thebase could be attached by welding or other mechanism of plasticdeformation, by screws or other mechanisms which will be obvious tothose skilled in the art. FIG. 6B shows the upper 12 portion of theanchor assembly while FIG. 6C shows a cross-section take along line6C-6C and FIG. 6D shows a cross section taken along line 6D-6D. FIG. 6Eshows the upper door 110 with insert 140 and rivet 130 that ispositioned in the upper 12 portion of the anchor assembly. A spacer ring6F is then positioned next in the anchor assembly and a cross section ofring 16 taken along line 6G-6G is shown in FIG. 6G. Next lower door 120with rivet 130 and insert 150 is loaded into the anchor assembly. Thelower 14 portion of the anchor base is seen in FIG. 61. When the lowerportion 14 is fastened to the upper 12 portion, the upper and lowerdoors 110, 120 and spacer 16 are captured therebetween. FIG. 6J shows across section of lower portion 14 taken along line 6J-6J and FIG. 6Kshows a cross section of lower portion 14 taken along line 6K-6K.

FIGS. 7A-7B show an alternative embodiment of assembling the anchoremploying a plurality of pins 17 penetrating the anchor cylinder wall,and extending beneath the lower rotating door 120. The pins coursethrough narrow channels 18 in the cylinder wall. Together, the pinsprovide a support that retain the moving members within the cylinder.FIG. 7A shows a cross section of the anchor assembled with all of itscomponents and FIG. 7B shows a bottom view of the anchor base withchannels 18. It is clear to those skilled in the art that thisembodiment may be combined with the embodiments shown in FIGS. 6A-6I andFIGS. 8A-8M. In embodiment of FIGS. 6A-6I, the pins would provide theadditional advantage of helping to retain the base of the cylinder. Inthe embodiment of FIG. 5, the pins provide further support for themoving members around the cutout that facilitates insertion of therotating doors 28.

FIGS. 8A-8M show an alternative embodiment of an anchor assemblyemploying a different assembly method. In this embodiment, the body ofthe cylinder is monolithic. The bottom of the cylinder has a shelf 26which retains the moving members. One side of the shelf is cut away 27so that the rotating doors may be inserted from below during assembly.Such an embodiment is most compatible with a cylinder body whichrecesses into the craniotomy, because in such embodiments the slot isnot impeded by the radial attachment tabs 20. To assemble thisembodiment, the upper rotating door 110 is slid into the central chamberof the cylinder. Next, the spacer 16 is inserted below the upperrotating door. Finally, the lower rotating door 130 is inserted. Oneside of the bottom of the cylinder is cutout 28 to facilitate slidingthe rotating doors and the spacer parts into the center of the cylinder.The rivets 130 may be attached to the rotating doors in sequence aftereach is inserted into the central chamber, or after both rotating doorshave been inserted. The rotating doors may be prevented from exiting thecentral chamber by tilting the slot slightly, so that the final door isstrained as it is inserted and then snaps into place, or by placing oneor more pins in the slot opening so as to constrain the motion of thelower door to rotational motion only. Alternatively, in both of theseembodiments, an extended shelf may be fixed in the entry slot. FIG. 8Ashows the anchor base that holds the upper 110 and lower 120 rotatingdoors. FIG. 8B shows a cross section of the anchor base of FIG. 8A takenalong line 8B-8B and FIG. 8C shows a cross section of the anchor basetaken along line 8C-8C. FIG. 8D shows the bottom of the anchor base andFIG. 8E shows the anchor base after upper door 110 has been insertedinto the base. FIG. 8F shows the anchor base after both upper 110 andlower 120 doors and spacer 16 have been loaded into the anchor base.FIGS. 8G-8L illustrate the sequence of loading components into theanchor base during assembly and FIG. 8M shows the assembled anchor.

FIGS. 9A-9C show cross section views, illustrating how set screws can bepositioned in three different positions, so as to impinge on the upperrotating door 110 alone, lower rotating door 120 alone, or on bothrotating doors 110, 120 simultaneously. Exemplary embodiments are shown,illustrating how the rotating doors may be fixed with standard setscrews. Small diameter screws, such as 0-80, are appropriate for thisapplication, because the cylinder body 10 is thin. A thin body 10 isdesired so that it does not protrude much above the surface of thecranium.

FIG. 9A shows a set screw 50 positioned to fix the upper rotating door110. In this embodiment, a flat set screw is used. The tip of such ascrew typically has a wide flat surface orthogonal to the screw's axisof symmetry, bounded by a narrow conical ring 51. When the screw isdeployed with its long axis tilted at approximately 30 degrees fromhorizontal, one edge of the conical ring is nearly parallel to the outeredge of the upper rotating door 110. As the screw is tightened, theconical ring 51 impinges upon the outer edge of the upper rotating door,but away from the lower rotating door 120.

FIG. 9B shows a similar set screw 52 positioned to fix the lowerrotating door 120. This screw is similar to the upper door fixationscrew 50, except that it is longer. FIG. 9C shows a set screw 54positioned so as to impinge upon both rotating doors 110 and 120simultaneously. In this embodiment a cone-point set screw isillustrated. Such a set screw has a wide conical ring 55 terminating atthe tip of the screw, with a tip angle of approximately 118 degrees.When the screw 54 is deployed with its long axis tilted approximately 60degrees from horizontal, it fixes both rotating doors.

FIGS. 10A-10J show an insertion tool 300 with handle 350 for placementand removal of inserts 140 and 150 into the rotating doors 110 and 120.FIGS. 10A-10F show portions of the tool 300 from several views. A sideview of the tool is seen in FIGS. 10A-10C and the tool is seen from atop view in FIGS. 10D-10F. FIGS. 10A and 10D show only the lowestportion, which interfaces directly with the insert, rotating door, andupper plate of the rivet. An orienting edge 320 at the bottom of thetool is complementary to the shape of the upper plate of the rivet 134.Tabs 310 at the bottom of the tool fit precisely into matching sockets132 in the upper portion of the rivets. In an alternative embodiment ofthe tool and the top of the rotating rivet, the tabs 310 are slightlylarger at their lower most position, and/or the sockets 132 are narrowerat their upper most position, to facilitate a snap fit of the tool withthe rivet rotor.

FIGS. 10B and 10E show a platform 340 at the base of theinsertion/removal tool. The platform forms a bridge between the smallfeatures and tight tolerances of the components shown in FIGS. 10A-10B,and the grip or handle 350 through which the surgeon applies torque, isshown in FIGS. 10C and 10F. In the embodiment illustrated, the grip 350is a hexagonal post with an angled handle, which may be turned digitallyor with a wrench. In other embodiments, the grip may take another form,for example, a cap screw. In another embodiment, it could be acylindrical post, with one or a plurality of radial holes into which alever arm can be inserted.

FIGS. 10G-10J show how the tool mates to the upper plate of the rivet134 and couples with an insert 150 on lower rotating door 120. The lowerportion of the tool has an angled shape 320 complementary to the edge ofthe upper plate of the rivet 134, to facilitate alignment of the toolwith the rivet, and to apply torque to the rivet as the tool is rotated.For fine positioning and additional torque, the tool has tabs 310 whichinsert into matching divots in the upper plate of the rivet 132. Acurved pin 335 holds an insert 140 or 150 in position next to the tool300 while the insert is placed into or removed from a rotating door 110or 120. A bulge 330 is provided for mounting the pin 335. This mountingbulge 330 is positioned so that it does not impinge upon the upperportion of the insert 140 as the tool is rotated.

FIGS. 11A-11D show the tool and insert through the cycle of positioning,attachment and detachment. In FIG. 11A, two insertion tools are abovethe anchor, and the inserts are seated in the rotating doors, retainedby the rivets. In FIG. 11B, the tools are lowered to a position adjacentto the upper portion of the rivets 134 and the inserts 140 and 150. Theinserts are seated in the rotating doors, retained by the rivets. InFIG. 11C, the tools have been rotated as indicated by the double headedarrows, so that the holding pins retain the inserts to the bottom of theinsertion tools. The rivets no longer retain inserts. In FIG. 11D, theinserts 140 and 150 are retained against the insertion tools by theholding pins 335 and lifted away from the rotating doors. The lowersurface of the insertion tool fits into divots 165 and 166, (not shown)in the inserts, so that the insert has a definite position relative tothe insertion tool. The rotating doors and rivets lie below the tool asthe tool is lifted away.

FIG. 12A-12C show an exemplary embodiment of the rotating doors adaptedfor intraoperative assembly. In FIG. 12A the rotating doors 110 and 120have gaps 71 positioned so that they can be passed around an indwellingmedical lead and placed in a receiving anchor base. The gaps 71 may bepositioned as in FIG. 12B, so that the doors may be passed around thelead in a single movement. Intraoperative handling is facilitated byholes 74 in the doors. Once inserted into the receiving base, the doorscan be rotated as in FIG. 12C in order to grip the medical lead. A snapmechanism can operate whereby a protrusion or detent from one door 73lodges into a cavity 72 on the other, so as to maintain the doors inapposition against the lead.

FIGS. 13A-13C show exemplary embodiments of the anchor base 10 and cap200 adapted for intraoperative assembly with doors such as shown inFIGS. 12A-12C. In the exemplary embodiment of FIG. 13C, base 10 has twotabs 20 for attachment to the cranium, but the number of tabs may bemodified as required. The doors pass around the lead, and they areplaced so that the lower door rests upon a shelf 26, and the upper doorrests upon the lower door. A retaining member, such as those illustratedin FIGS. 14A-14E may optionally be inserted interfacing with an annulargroove 41 in such a way as to partially occlude the lumen of the base 10and prevent removal of the rotating doors. Two embodiments of the cap200 are shown in FIGS. 13A and 13B, with pins 220 placed so that the cap200 can be attached to the base 10 by protrusions 225 from the pins 220into the annular groove 41. In the embodiment of FIG. 13B, cavities 226are placed in the cap 200, so as to extend the effective length of thepins 220 and control the strain of the pin and mating forces, as will befamiliar to those skilled in the art. The annular groove 41 can also bea point of attachment for additional instruments used intraoperativelysuch as a positioning guide or other reference instruments often usedduring neurosurgery. The retaining member may similarly be modified topermit attachment of other instruments used intraoperatively. The base10 and cap 200 could optionally have features to force a particularalignment of the cap and base. For example, a pin may extend from thecap and seat in a groove on the base.

FIGS. 14A-14E show several exemplary embodiments of a retaining memberwhich may be placed intraoperatively, so as to hold or retain the doorswithin the base. All of these embodiments include a hole feature tofacilitate manipulation of the member. One embodiment 400 is aconventional retaining ring, as will be well familiar to those skilledin the art and this is seen in FIG. 14A. In FIG. 14B, retaining member410 includes a member 415 to increase the security of placement of theretention member. Additional security may be desirable if mountingfeatures for a cap or intraoperative instruments are added to theretention feature. In FIG. 14C, the retaining member 420 occupies half,more or less, of the annular groove, so as to generate less interferencewith a medical lead placed in the lumen of the base. In FIGS. 14D and14E the ends of retaining members 430 and 440 interface with a groove,such as 41 of FIG. 13C, but the body of these retaining members crossthrough the lumen of the base. Such disposition of the body of theretaining member keeps the groove free to accept other attachments.Retaining member 430 passes straight across, while retaining member 440curves away from the center, so that it is clear of the center duringplacement. The depictions of retaining members 430 and 440 also includematerial 450 above the plane of the annular groove. Such material may bearranged so as to strengthen or stiffen the retaining member, or tointerface with other parts.

FIGS. 15A-15D show an embodiment where retaining member 460 has pins 220extending in such a way that they could snap into the cap 200 andthereby attach it to the base 10. FIG. 15A is a perspective view of theanchor base 10 with retaining member 460 and cap 200 assembled together.FIG. 15B shows cap 200 and FIG. 15C shows the retaining member 460.Anchor base 10 is seen in FIG. 15D. FIG. 16 is a perspective view ofanchor base 10 with the doors 110 and 120 and retaining member 440assembled together. The retaining member 440 scats into an annulargroove 41, but its body is within the center of the base, leaving muchof the groove 41 clear.

While the exemplary embodiments have been described in some detail forclarity of understanding and by way of example, a variety of additionalmodifications, adaptations and changes may be clear to those of skill inthe art. Hence, the scope of the present invention is limited solely bythe appended claims.

What is claimed is:
 1. A method of securing an implantable lead intotissue of a patient, the method comprising: positioning a base having anupper surface, a lower surface and a central passage with a central axistherebetween adjacent a craniotomy in a skull of the patient; securingthe base to the skull; inserting an implantable lead through the centralpassage and into the tissue; rotating a first rotating member coupledwith the base so as to meet and engage the implantable lead at aplurality of positions within the central passage, wherein the firstrotating member rotates around the central axis; and rotating a secondrotating member coupled with the base so as to meet and engage theimplantable lead at a plurality of positions within the central passage,wherein the second rotating member rotates around the central axis,wherein the first and second rotating members rotate independently ofone another, and wherein rotating the first rotating member in a firstdirection and rotating the second rotating member in a second directionopposite the first direction engages and captures the implantable leadtherebetween.
 2. A method according to claim 1, further comprisingrotationally adjusting the first and second rotating members in order tocapture the lead therebetween or to release the lead therefrom.
 3. Amethod according to claim 1, further comprising removing an insertcoupled to the first or second rotating members, the insert releasablycoupled with the lead.
 4. A method according to claim 1, furthercomprising attaching an insert to the first or second rotating members,the insert releasably coupleable with the lead.
 5. A method according toclaim 1, wherein securing the base comprises press fitting at least aportion of the base into the craniotomy.
 6. A method according to claim1, wherein securing the base comprises coupling the base to the skullwith a fastener.
 7. A method according to claim 6, wherein the fasteneris a screw.
 8. A method according to claim 1, wherein securing the basecomprises recessing at least a portion of the base in the craniotomy. 9.A method according to claim 1, wherein securing the base comprisescoupling the base adjacent to the craniotomy so that a bottom surface ofthe base is substantially flush with a top surface of the skull.
 10. Amethod according to claim 1, further comprising placing a cover intoengagement with the base so as to substantially cover the centralpassage and capture the implantable lead therebetween.
 11. A methodaccording to claim 1, wherein the implantable lead comprises anelectrode.
 12. A method according to claim 1, wherein the implantablelead is a catheter.
 13. A method according to claim 1, furthercomprising retaining the first rotating member within the base.
 14. Amethod according to claim 13, wherein the step of retaining comprisesplacing a retaining member in the base.
 15. A method according to claim1, further comprising locking the first and second rotating memberstogether so as to prevent relative motion therebetween.
 16. A methodaccording to claim 15, wherein locking the first and second rotatingmembers comprises threadably engaging the first and second rotatingmembers with a set screw.
 17. A method according to claim 1, furthercomprising positioning the lead into a channel in the upper surface or achannel of the cover.
 18. A method according to claim 1, furthercomprising applying a potting material to fill gaps between the base andthe craniotomy, thereby reducing or eliminating leakage of body fluidsaround the base.
 19. A method according to claim 1, further comprisingdelivering a current through the lead to the tissue.
 20. A methodaccording to claim 1, further comprising delivering a therapeutic agentthrough the lead to the tissue.